Flavor ingredient regulatory record
4-(Methylthio)-4-methyl-2-pentanone
4-(Methylthio)-4-methyl-2-pentanone is a thiol in the sulfur family, FEMA GRAS under FEMA number 3376 (CAS 23550-40-5).
- FEMA
- 3376
- CAS
- 23550-40-5
- JECFA
- 500
- EU FL
- 12.058
- Formula
- C7H14OS
GRAS status: FEMA GRAS, publication 6. Recorded by FDA in the Substances Added to Food inventory under CAS 23550-40-5.
Structure
Identity
Also known as: 2-Pentanone, 4-methyl-4-(methylthio)-, 4-Methyl-4-(methylthio)-2-pentanone, 4-Methylmercapto-4-methylpentan-2-one, 4-methylthio-4-methyl-2-pentanone, 2-pentanone, 4-methyl-4-(methylthio)-, 4-methyl-4-(methylthio)-2-pentanone, 4-methyl-4-(methylthio)pentan-2-one, 4-methyl-4-(methylsulfanyl)pentan-2-one, 4-methylmercapto-4-methylpentan-2-one, 4-methylthio-4-methyl-2-pentanone [fhfi], 4-methyl-4-methylthio-2-pentanone, 4-methyl-4-methylsulfanylpentan-2-one.
Can 4-(Methylthio)-4-methyl-2-pentanone be labeled natural?
4-(Methylthio)-4-methyl-2-pentanone occurs in nature, so the label depends on the route: 4-(Methylthio)-4-methyl-2-pentanone won from a natural source by a physical, enzymatic or microbiological process is natural flavor in the United States, and synthesized 4-(Methylthio)-4-methyl-2-pentanone is artificial. In the EU and UK the natural claim likewise needs the natural route, while Mercosur and Mexico keep a third class, identical-to-natural, for the synthetic material.
- United States
- Natural or artificial, by process
- European Union and UK
- Natural only from natural material
- Mercosur and Mexico
- Natural or identical-to-natural
How each market defines the classes: natural vs artificial flavor under 21 CFR 101.22.
Regulatory status, with citations
United States
4-(Methylthio)-4-methyl-2-pentanone is FEMA GRAS under FEMA number 3376. It is cited in the Code of Federal Regulations at 21 CFR 172.515.
European Union and United Kingdom
Listed on the Union List of flavouring substances as FL 12.058, Annex I Part A under Regulation (EC) 1334/2008, evaluation status approved (JECFA). The UK retains the same list.
JECFA (WHO / FAO)
JECFA number 500, evaluated at the 53rd meeting in 1999. No safety concern at current levels of intake when used as a flavouring agent.
Other US flags
Not on the California Proposition 65 list.
TSCA Inventory status
A flavor ingredient is also an industrial chemical. 4-(Methylthio)-4-methyl-2-pentanone appears on the EPA Toxic Substances Control Act Chemical Substance Inventory under CAS 23550-40-5, where EPA names it 2-Pentanone, 4-methyl-4-(methylthio)-.
Active in US commerce
EPA designates this substance active, so no Notice of Activity Form B is required before manufacturing. What active and inactive mean.
EPA publishes no regulatory flags on this listing. What the flags mean.
From the EPA non-confidential TSCA Inventory, July 2026 release. EPA also maintains a confidential portion it does not publish. Search the Inventory by CAS number.
Odor and taste
Taste: Savory, pungent, umami.
Where it is used
4-(Methylthio)-4-methyl-2-pentanone is used in savory dishes, seasoning, condiments and snacks, typically as a sulfur note.
Structurally similar flavor ingredients
Flavor ingredients with a GRAS determination closest to 4-(Methylthio)-4-methyl-2-pentanone by structure. Whether one can replace it is a sensory and regulatory call; the reformulation tool works that through.
| Material | FEMA | Similarity | Occurrence |
|---|---|---|---|
| 3,3,5-Trimethyl cyclohexanol | 3962 | 74% | In nature |
| 4-Mercapto-4-methyl-2-hexanone | 4583 | 73% | Not determined |
| 2,2,6-Trimethyl-6-vinyltetrahydropyran | 3735 | 72% | In nature |
| (+/-)-2-Mercaptomethylpentan-1-ol | 3995 | 62% | Not determined |
| Isophorone | 3553 | 60% | In nature |
More thiols in this index
2-Mercaptopropionic acid · 2-Naphthalenethiol · 3-Mercaptopropionic acid · 4-(Methylthio)butanal · 2-Thienyl disulfide · Methyl 3-methyl-1-butenyl disulfide
4-(Methylthio)-4-methyl-2-pentanone FAQ
Does 4-(Methylthio)-4-methyl-2-pentanone have FEMA GRAS status?
4-(Methylthio)-4-methyl-2-pentanone holds FEMA GRAS status under FEMA number 3376. It is also codified at 21 CFR 172.515.
How do I cite 4-(Methylthio)-4-methyl-2-pentanone by FEMA or CAS number?
Cite 4-(Methylthio)-4-methyl-2-pentanone as FEMA 3376 or CAS 23550-40-5; both point to the same entry. FEMA files it in the sulfur flavor category.
Can 4-(Methylthio)-4-methyl-2-pentanone be labeled a natural flavor?
Since 4-(Methylthio)-4-methyl-2-pentanone is found in nature, US labeling follows how it was obtained: natural flavor from a natural source and a natural process, artificial when 4-(Methylthio)-4-methyl-2-pentanone is synthesized. In the EU and UK the natural claim likewise needs the natural route, while Mercosur and Mexico keep a third class, identical-to-natural, for the synthetic material.
Can 4-(Methylthio)-4-methyl-2-pentanone be used in the EU and UK?
4-(Methylthio)-4-methyl-2-pentanone is on the EU Union List of flavouring substances as FL 12.058 (Annex I Part A) under Regulation 1334/2008.
Has JECFA evaluated 4-(Methylthio)-4-methyl-2-pentanone?
Yes. JECFA number 500, evaluated at the 53rd meeting in 1999. Conclusion: No safety concern at current levels of intake when used as a flavouring agent.
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Sources and attribution. The identity and regulatory facts on this page are taken from the FDA Substances Added to Food inventory, a US government record, which lists this substance as 4-(METHYLTHIO)-4-METHYL-2-PENTANONE under CAS 23550-40-5 and carries its FEMA number, its JECFA flavor number. The inventory is searchable at FDA. FDA records its technical effect as flavoring agent or adjuvant.
A FEMA GRAS conclusion is reached by the Expert Panel of the Flavor and Extract Manufacturers Association of the United States, and the FEMA number names that conclusion. FEMA publishes its own entry for this substance in the FEMA Flavor Library, which is the authoritative record of what the Panel decided and is worth reading alongside this page.
Ambrose Compliance is not affiliated with, endorsed by, or sponsored by FEMA. FEMA and FEMA GRAS are used here as identifiers for a published regulatory determination, not as marks of any relationship between FEMA and Ambrose.
About this page. Facts come from the FDA Substances Added to Food inventory, the Code of Federal Regulations, the EPA TSCA Inventory, the EU Union List, JECFA and the Ambrose database, with FEMA's published determination cited where it applies; parts of the text are written by Ambrose AI, which can make mistakes. Check the cited source before relying on anything here. This is not regulatory or legal advice.